Dust aerosol radiative effects during summer 2012 simulated with a coupled regional aerosol–atmosphere–ocean model over the Mediterranean

Abstract

Abstract. The present study investigates the radiative effects of dust aerosols in the Mediterranean region during summer 2012 using a coupled regional aerosol-atmosphere-ocean model (CNRM-RCSM5). A prognostic aerosol scheme, including desert dust, sea salt, organic, black-carbon and sulphate particles, has been integrated to CNRM-RCSM5 in addition to the atmosphere, land surface and ocean components. An evaluation of this aerosol scheme of CNRM-RCSM5, and especially of the dust aerosols, has been performed against in situ and satellite measurements, showing its ability to reproduce the spatial and temporal variability of aerosol optical depth (AOD) over the Mediterranean region in summer 2012. The dust vertical and size distributions have also been evaluated against observations from the TRAQA/ChArMEx campaign. Three simulations have been carried out for summer 2012 with CNRM-RCSM5, including the full prognostic aerosol scheme, only monthly-averaged AOD means from the aerosol scheme or no aerosols at all, in order to focus on the radiative effects of dust particles and the role of the prognostic scheme. Surface short-wave aerosol radiative forcing variability is found to be more than twice as high over regions affected by dust aerosols, when using a prognostic aerosol scheme instead of monthly AOD means. In this case downward surface solar radiation is also found to be better reproduced according to a comparison with several stations across the Mediterranean. A composite study over 14 stations across the Mediterranean, designed to identify days with high dust AOD, also reveals the improvement of the representation of surface temperature brought by the use of the prognostic aerosol scheme. Indeed the surface receives less radiation during dusty days, but only the simulation using the prognostic aerosol scheme is found to reproduce the observed intensity of the dimming and warming on dusty days. Moreover, the radiation and temperature averages over summer 2012 are also modified by the use of prognostic aerosols, mainly because of the differences brought in short-wave aerosol radiative forcing variability. Therefore this first comparison over summer 2012 highlights the importance of the choice of the representation of aerosols in climate models.

Optical, physical and chemical properties of aerosols transported to a coastal site in the western Mediterranean: a focus on primary marine aerosols

“…It should be noted that the DRE of aerosols in the longwave (LW) spectral range, which can counterbalance a part of the SW cooling at TOA, is not estimated here. Contrary to the LW DRE of mineral dust exerted near dust sources, this effect is generally lower than SW DRE during the transport of mineral dust over the Mediterranean Basin (Nabat et al, 2015). In the same way as at the surface, Fig.…”

Direct radiative effects during intense Mediterranean desert dust outbreaks

“…However, the obtained results were representative at a local scale and, considering the high spatial variability of desert dust outbreaks, the optimum solution of assessing in a comprehensive way their impacts on weather and climate is provided by atmospheric-dust models. To this end, the induced DREs by the Mediterranean desert dust outbreaks have been analysed through short-term numerical simulations (Pérez et al, 2006;Santese et al, 2010;Remy et al, 2015) while similar studies have been conducted either at a seasonal (Nabat et al, 2015a) and annual scale (Nabat et al, 2012) or for extended time periods (Spyrou et al, 2013;Nabat et al, 2015b), pointing out the key role of desert dust aerosols in the Mediterranean climate.…”

“…Spyrou et al, 2013), limited time periods (e.g. Nabat et al, 2015b) or specific desert dust outbreaks (e.g. Pérez et al, 2006;Santese et al, 2010;Stanelle et al, 2010).…”

In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

“…Alpert et al, 1998;Chaboureau et al, 2011); radiative budget and climate (e.g. Nabat et al, 2012Nabat et al, , 2015a; precipitation chemistry (Chester et al, 1996;Loÿe-Pilot et al, 1986;Avila and Rodà, 2002); soil formation (Nihlén et al, 1995); and biogeochemistry of forest ecosystems (Avila and Peñuelas, 1999), oligotrophic lakes (Morales-Baquero et al, 2006;Reche et al, 2009), and marine surface waters (Guerzoni et al, 1999;Herut et al, 1999;Guieu et al, 2014).…”